Imran - 8
Joeseph - 10
Test1 - 6
Test2 - 4
Joeseph - 5
Aaron - 4
Test1 - 1
Zzron - 1
Joeseph - 3
Test1 - 10
Joeseph - 4

with open("highscores.txt", "r+")as file:
    file.seek(0)
    scores = file.readlines()

user_scores = {}
for line in scores:
    name, score = line.rstrip('n').split(' - ')
    score = int(score)
    if name not in user_scores or user_scores[name] < score:
        user_scores[name] = score

for name in sorted(user_scores):
    print(name, '-', user_scores[name])

Joeseph - 5